In order to transfer images of a pattern of an electronic circuit onto a work such as a printed circuit board, a liquid crystal panel and a color filter for liquid crystal, a various exposure apparatus have been proposed to expose a work to light by radiating ultraviolet light having a predetermined wave length. Such exposure apparatus include so-called semiautomatic exposure apparatus wherein a work is manually loaded and unloaded by a worker and so-called automatic exposure apparatus wherein a work is automatically operated from load to unload of the work.
One example of a semiautomatic exposure apparatus is disclosed in Japanese Laid-open Patent Application No. 8-43950 (see columns [0043] to [0082]) and is explained with reference to FIG. 14. FIG. 14 is a schematic view of a conventional semiautomatic exposure apparatus. As shown in FIG. 14, a semiautomatic exposure apparatus 100 includes: a conveyor mechanism 103 which reciprocally conveys first and second tables 101, 102 for supporting a work between a load/unload position H1 and an under exposure position R1; a hoist mechanism 104 which elevates a support plate 101a (102a) of one table 101 (102), on which a work W and a mask M are placed, to an exposure position R2 after the table 101 (102) is carried by the conveyor mechanism 103 from the load/unload position H1 to the under exposure position R1, and lowers the other support plate 102a (101a), on which a work W and a mask M are placed, positioned in the exposure position R2 to the under exposure position R1 to place the support plate. 102a (101a) onto the table 102 (101); an upper frame 105 which sucks and supports one of the support plates 101a, 102a elevated by the hoist mechanism 104; a light-exposure mechanism 107 which radiates light such as ultraviolet light onto the upper frame 105 through an optical system 106; and imaging means 108, an alignment table 109 and a mask-support mechanism 110 arranged in the load/unload position H1.
In operation of the semiautomatic exposure apparatus (hereinafter referred to as an exposure apparatus) 100, the worker places a work W onto the support plate 101a of the first table 101 that is positioned in the load/unload position H1, and at the same time, the worker sets a mask M in conformity with the work W. The imaging means 108 pictures the alignment marks (not shown) of the mask M and the work W. When the work W is moved for alignment, the mask-support mechanism 110 sucks the mask M and displaces at least a part of the mask M for a certain distance from the work W, during which the alignment table 109 moves the support plate 101a for the purpose of alignment. The mask-support mechanism 110 is then lowered to superpose the mask M on the work W. If the both alignment marks (not shown) pictured by the imaging means 108 are within the allowable range, the alignment operation of the mask M and the work W is completed. The worker then fixes the mask M on the support plate 101a with the use of fixing means such as adhesive tapes.
Next, the conveyor mechanism 103 is actuated, so that the first table 101 in the load/unload position H1 is carried toward the under exposure position R1, while the second table 102 in the under exposure position R1 is carried toward the load/unload position H1. The hoist mechanism 104 elevates the support plate 101a of the first table 101 that is carried in the under exposure position R1 so that the support plate 101a mates with the upper frame 105 arranged in the exposure position R2 with the aid of vacuum. The light-exposure mechanism 107 then radiates light through the optical system 106 to the mask M and the work W that are sandwiched between the upper frame 105 and the support plate 101a, so that the images of the pattern of the mask M are transferred onto the work W.
After the exposure operation is completed, the vacuum seal between the upper frame 105 and the support plate 101a is disengaged, and the work W and the mask M are released from the upper frame 105. The work W and the mask M are received by the hoist mechanism 104 in a manner to be placed onto the support plate 101a, and are lowered to the first table 101 positioned in the under exposure position R2 by the lowering motion of the hoist mechanism 104.
During the exposure operation, the alignment operation of a work W and a mask M are carried out in the load/unload position H1 relative to the second table 102 in a manner similar to the alignment operation on the fist table 101.
Therefore, the alignment operation is carried out at one of the first and second tables 101, 102 positioned in the load/unload position H1, while the exposure operation is carried out in the exposure position R2 relative to the other second and first tables 102, 101 positioned in the under exposure position R1, so that the alignment operation and the exposure operation are alternately and repeatedly carried out. It should be noted that the first table 101 and the second table 102 are positioned in a different height at the under exposure position R1. However, the support plates 101a, 102a of the fist and second table 101, 102 can engage with and disengage from the upper frame 105 by way of varying the stroke length (hoist distance) of the hoist mechanism 104.
In another known exposure apparatus, the exposure operation is carried out in the underexposure position R1 of the semiautomatic exposure apparatus 100. In this exposure apparatus, both tables are constructed such that a light-transmissible plate which retains a mask is opened and closed to allow a work to be set in a position facing to the mask. In this exposure apparatus, a suitable exposure operation is carried out for a work on both tables that are alternately transferred in a different height of the underexposure position, by way of varying the exposure time relative to the respective tables.
However, the conventional exposure apparatus have the following drawbacks.
(1) Since the support plate to be alternately transferred by the first and second tables and separated from the tables is elevated through the hoist mechanism so as to set a work in the exposure position with the work mating with the upper frame, it is difficult to retain the alignment position between the work and the mask until they are set in the exposure position. Further, since both tables are carried at different height levels in the load/unload position, the alignment operation has to be carried out at different height levels. This requires a further operational control when compared with the alignment operation carried out on the alignment table at the same height.
(2) Since a metal frame is provided in a manner surrounding the light-transmissible plate that is adjacent to the mask, a setting operation of the light-transmissible plate is required whenever the light-transmissible plate is replaced or initially set up.
(3) During the alignment operation of the mask and the work, the work is moved for alignment while the mask is retained by the mask-support mechanism 110. However, this requires a complicated structure. Further, the worker fixes the mask and the work by means of adhesive tapes, leading to increased number of operations of the worker.
(4) At the time of alignment of the mask with the work, the worker has to set both the mask and the work, which makes the load/unload operation complicated. In the exposure apparatus of the type in which the light-transmissible plate can be open and closed for the placement of a work, the open/close motion of the light-transmissible plate requires a great effort for the worker, and further, the imaging means has to be retracted so as not to bump against the light-transmissible plate during the open/close motion of the light-transmissible plate.
(5) The conventional exposure apparatus includes a mechanism which alternately carries both tables between the load/unload position and the exposure position through the two transferring passages arranged one on top of the other, and a mechanism which separates the tables from the conveyor mechanism to carry out the alignment operation and the exposure operation at the load/unload position and the exposure position, respectively. Therefore, the conventional exposure apparatus requires the control of the vertical movement of the support plate as well as a large driving force to move the support plate.
In view of the above, the present invention seeks to provide an exposure apparatus and an exposing method wherein the alignment position and the exposure position of the works are substantially the same in height direction, and wherein the metal frame surrounding the light-transmissible plate can be omitted, and wherein the operation of the light-transmissible plate where a mask is set is readily performed.